Generally, an automatic transmission (AT) includes a torque converter and a powertrain of a multiple speed gear mechanism connected to the torque converter. In addition, a hydraulic control system is provided with an AT for selectively operating at least one operational element included in the powertrain, based on the running state of the vehicle.
Such an AT also includes a hydraulic pressure source supplying a hydraulic pressure, a main line connected to the hydraulic pressure source in order to guide the hydraulic pressure, distributing lines branching from the main line in order to respectively guide the hydraulic pressure to the operational elements, and a valve provided respectively at the distributing lines in order to control the hydraulic pressure inflowing into the operational elements. In addition, to control a main line hydraulic pressure (hereinafter called “line pressure”), a conventional AT typically uses a mechanical control means controlling the line pressure according to a map table predetermined on the basis of only a throttle valve opening.
However, such a mechanical control means has the following problem. Since the line pressure is controlled according to the map table predetermined on the basis of only a throttle valve opening, a problem can occur in that dynamic characteristics of the hydraulic pressure inflowing into the operational elements is deteriorated.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.